As shown in FIGS. 1-3, a water tank 10 of the prior art toilet has a flush handle 11 for controlling two pull rods 12, 122, which are capable of actuating two chains 13 which are in turn fastened with two covers 16 and 17 of two water discharging tubes 14 and 15. The chains 13 are provided at both ends thereof with a C-shaped ring 18 in contact with the pull rods 12, 122 and the covers 16 and 17.
In this prior art toilet, both ends of the chains 13 cannot be located easily and precisely with the pull rods 12, 122 and the covers 16 and 17, and that the chains 13 cannot be easily adjusted in length in accordance with the distances between the pull rods 12, 122 and the covers 16, 17, and further that the C-shaped ring 18 is vulnerable to damage or deformation.